When did Bitcoin Core deprecate the mining function?

Question

I understand that bitcoin clients originally allowed users to run their own node and mine. This was back when mining was mainly GPU-based.

When was the mining functionality removed from Bitcoin Core?

Answer 1

Arguably, never: Bitcoin Core still has a rudimentary mining function built-in, as it is used for testing purposes (on testing networks where the difficulty is lower). CPU mining has however been entirely pointless since GPU mining became ubiquitous, around the end of 2010. Since then, features and optimizations related to CPU mining have been removed from, and moved out of, Bitcoin Core.

There have roughly 5 different ways to interact with the mining functionality:

• The built-in background miner, accessed through GUI, by just enabling a checkbox "generate". This was available in the very first release. I'm not sure when it was removed, but at the latest in 2016.
• The built-in background miner, accessed through the setgenerate RPC. This RPC was added on 2010 Feb 23, and removed on 2016 Mar 14.
• The synchronous miner, accessed through RPCs like generate and generatetoaddress, which don't run in the background, but just run a relatively small number of POW operations, and return the constructed blocks through RPC. The purposes is testing, and using these on mainnet will almost certainly just fail to construct anything. The generate RPC call was introduced on 2015 Apr 9, and while that specific RPC doesn't exist anymore, more recent incarnations of it like generatetoaddress still exist in the codebase today.
• The getwork RPC protocol allows mining in an external process was introduced on 2010 Nov 23, and removed on 2014 Jun 21, as it was superseded by getblocktemplate.
• The more advanced getblocktemplate (BIP22) RPC protocol was added on 2012 May 12, still exists in the codebase today, and is the primary way through which mining pools interact with the Bitcoin network.

After 2010, various optimizations for faster CPU mining that existed in the codebase have also been gradually removed, as they were irrelevant for mining for test purposes, and added a maintenance burden.

Answer 2

The mainnet mining capability was removed in 0.13.0, The release note is dated 23 August 2016

https://bitcoin.org/en/release/v0.13.0#removal-of-internal-miner

Removal of internal miner

As CPU mining has been useless for a long time, the internal miner has been removed in this release, and replaced with a simpler implementation for the test framework.

The overall result of this is that setgenerate RPC call has been removed, as well as the -gen and -genproclimit command-line options.

For testing, the generate call can still be used to mine a block, and a new RPC call generatetoaddress has been added to mine to a specific address. This works with wallet disabled.